Effects of Soil Salt Stress on Seed Germination and Plant Growth of Ipomoea aquatic Forsk.

Objective This study aimed to investigate the effects of soil salt stress on the seed germination, seedling growth, and physiological metabolism of Ipomoea aquatica Forsk., in order to provide a theoretical basis for evaluating its adaptability and optimizing cultivation management in saline-affected soils.

Methods Through laboratory germination tests and pot experiments, different salt concentration gradients were established. The germination rates and salt injury index of Ipomoea aquatica Forsk. seeds, along with seedling emergence rate, plant height, leaf number, and dry matter accumulation, were measured. Changes in chlorophyll contents, proline levels, ion uptake (K⁺, Na⁺), and nitrogen and phosphorus nutrient contents were also analyzed.

Results The results showed that the seed germination rate of Ipomoea aquatica Forsk. significantly decreased as salt concentration increased, while the salt injury index significantly increased (P < 0.05). Germination was completely inhibited at 2.0% NaCl. Seedling growth was markedly suppressed under soil salt stress. Emergence rate, plant height and leaf number all declined as salinity increased. Dry matter accumulation increased under low and moderate salt conditions but decreased sharply under high salt stress (ECe ≥ 8.0 dS m⁻¹). In terms of physiological metabolism, chlorophyll content continuously decreased, with a maximum reduction of 20.4%, while the proline content significantly increased (P < 0.05), approximately twice that of the control, under ultra-high salt conditions. Ion homeostasis was severely disrupted under high salt stress, with the Na⁺/K⁺ ratio significantly increasing to 0.79 (P < 0.05). Furthermore, the total nitrogen content of the plants decreased significantly, whereas the total phosphorus content continued to accumulate.

Conclusion Ipomoea aquatica Forsk. exhibits a certain degree of tolerance to low and moderate salt concentrations. However, high salt stress severely inhibits its germination and growth, leading to ion imbalance and metabolic disruption. In practical cultivation on saline soils, salinity regulation and resistance management are necessary to enhance its adaptive capacity.